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(I) Multiple Choices. Please choose the one alternative that best answers the question. (56%, 2% of each)

(1) One nanogram doesn't seem like a very large number. How many magnesium atoms are there in

1 .OO ng of magnesium?

(A) 4.11 x 1012 atoms (B) 2.48 x lot3 atoms (C) 6.83 x 11" atoms

(D) 6.02 x l0I4 atoms (E)1.46 x 1 0 ' ~ atoms

(2) The Hall process for the production of aluminum involves the reaction of aluminum oxide with elemental carbon to give aluminum metal and carbon monoxide. If the yield of this reaction is 82%

and aluminum ore is 71% by mass aluminum oxide, what mass of aluminum ore must be mined in

order to produce 1.0 x lo3 kg of aluminum metal by the Hall process?

(A) 1.8 lo3 kg (13) 2.2 lo3 kg (c) 1.1 103 kg

(13) 1.6 x lo3 kg (E) 3.3 lo3 kg

(3) Which of the following compounds is a weak electrolyte?

(A) HCI (B) CH3COOH (C) C6H1206 (Dl 0 2 (E) NaCl

(4) When 20.0 mL of a 0.25 M (NH4)2S solution is added to 150.0 mL of a solution of CU(NO~)~, a CuS precipitate forms. The precipitate is then filtered fiom the solution, dried, and weighed. If the

recovered CuS is found to have a mass of 0.3491 g, what was the concentration of copper ions in the

original Cu(NO3)2 solution?

(A) 3.65 x M (B) 1.22 x loq2 M

@) 4.87 x M (E) 2.43 x M

(5) Air contains 78% N2,21% 02, and 1% Ar by volume. What is the density of air at 1,000 torr and

-10 "C?

(A) 1.3 glL (E) 0.56g /L

(6) Whichstatementisfalse?

(A) The average kinetic energies of molecules fiom samples of different "ideal" gases are the same at

the same temperature.

(B) The molecules of an ideal gas are relatively far apart.

(C) All molecules of an ideal gas have the same kinetic energy at constant temperature.

@) Molecules of a gas undergo many collisions with each other and the container walls.

(E) Molecules of greater mass have a lower average speed than those of less mass at the same

temperature.

(B) 2.6 g/L (C) 3.5 g/L

(C) 3.33 x M

-

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(7) A 100.0 mL sample of 0.2 M aqueous hydrochloric acid is added to 100.0 mL of 0.2 M aqueous

ammonia in a calorimeter whose heat capacity (excluding any water) is 480 JK. The following

reaction occurs when the two solutions are mixed.

HCl(aq) + W 3 ( a q ) + m4Cl(aq)

The temperature increase is 2.34"C. Calculate AH per mole of HCl and NH3 reacted.

(A) 154 kJ1mol (l3) 1.96 Wmol (C) 485 Wmol (D) -1.96 kJ1mol (E) -154 kJ/mol

(8) The atomic radius of sodium is 186 pm and of chlorine is 100 pm. The ionic radius for ~ a + is 102 pm

and for C1' is 18 1 pm. In going fiom Na to C1 in Period 3, why does the atomic radius decrease while

the ionic radius increases?

(A) The inner electrons in the sodium cation shield its valence electrons more effectively than the

inner electrons in the chloride anion do.

(B) The inner electrons shield the valence electrons more effectively in the chlorine atom than in the

chloride anion.

(C) The outermost electrons in chloride experience a smaller effective nuclear charge than those in the

sodium cation do.

@)The outermost electrons in chloride experience a larger effective nuclear charge than those in the

sodium cation do.

(E) Monatomic ions are bigger than the atoms from which they are formed.

(9) Examine the phase diagram for the substance Bogusium (Bo) and select the correct statement.

(A) Bo(,) has a lower density than BO(~. (B) The triple point for Bo is at a higher temperature than the melting point for Bo.

(C) Bo changes fiom a solid to a liquid as one follows the line fiom C to D. (D) Bo changes from a liquid to a gas as one follows the line fiom C to D.

(E) Point B represents the critical temperature and pressure for Bo.

10) Ozone (03) in the atmosphere can be reacted with nitric oxide (NO) to produce oxygen gas and

nitrogen dioxide. What is the enthalpy change when 8.50L of ozone at a pressure of 1 .OO atrn and

25°C reacts with 12.0 L of nitric oxide at the same initial pressure and temperature? [AHOr(NO) = 90.L

kJImol; AH0r(N02) = 33.85 Wmol; AH0A03) = 142.2 Wmol]

(A) -69.2 kJ (B) -19.7 kJ (C) -1 690 kJ @) -97.6 kJ (E) -167 kJ

11) Green light has a wavelength of 520 nrn. Calculate the energy of one photon of green light.

( A ) 3 . 4 ~ 1 0 " ~ ~ ( l 3 ) 3 . 4 ~ 1 0 " ~ ~ ( C ) 3 . 8 ~ 1 0 - ~ ~ ~ @ ) 3 . 4 ~ 1 0 - ~ ' ~ (E) 3.8 x 10- l~ J

12) The longest wavelength of light that causes electrons to be ejected from the surface of a copper plate

is 243 nm. What is the maximum velocity of the electrons ejected when light of wavelength 200 nrn

shines on a copper plate?

(A) 1.48 x 1 o6 mls (C) 4.67 x lo4 m/s

@)1.97 x lo4 d s

(B) 6.22 x 10' m/s

(E) 1.34 x lo6 m/s

13) Which one of the following sets of quantum numbers is not possible? n 1 mr

14) Consider the species ~ l 2 + , C12, and C12-. Which of these species will be paramagnetic?

(A) Only Cl2 (B) ~ 1 2 ' and C12 (C) C12, and Clz-

(D) ~ 1 2 + and Cl2- (E) All three are paramagnetic

15) Potassium bromide, KBr, crystallizes like NaCl in a face-centered lattice. The ionic radii of K+ and

Br- ions are 133 pm and 195 pm, respectively. Assuming that all Br- ions are positioned in the face and comers of the unit cell, while the K+ ions are positioned along the edge alternating between

anions, calculate the length of a unit cell edge.

(A) 230 pm (B) 328 Pm (C) 523 pm (D) 656 pm (E) 780 pm

16) The thermal decomposition of acetaldehyde, CH3CH0 + CH4 + CO, is a second-order reaction.

The following data were obtained at 51 8OC.

Time (s) Pressure CH3CH0 (--Hi)

Based on the data given, what is the half-life for the disappearance of acetaldehyde?

(A) 1.5 x lo5 s (B) 410 s (c) 5.4 lo7 (D) 520 s (E) 305 s

17) Which of the following is a true statement about chemical equilibria in general?

(A) At equilibrium the total concentration of products equals the total concentration of reactants.

(B) Equilibrium is the result of the cessation of all chemical change.

(C) There is only one set of equilibrium concentrations that equals the K, value.

(D) At equilibrium, the rate constant of the forward reaction is equal to the rate constant for the

reverse reaction.

(E) At equilibrium, the rate of the forward reaction is equal to as the rate of the reverse reaction.

18) An-ange the acids HF, HCI, H2S04 and HN03 in order of increasing acid strength.

(A) HF < HC1< HN03 < (B) HCl< HF < H2S04 < HN03

(C) HCl < HN03 < H2S04 < HF @) HF < HN03 < H2S04 < HC1

(E) HF < H2S04 < HC1< HNO3

19) Arrange the following substances in the order of increasing entropy at 25OC.

HF@), NaF(s), SiF4(,), SiH4@), Al(s)

(20) Sodium carbonate can be made by heating sodium bicarbonate:

Given that AH0 = 128.9 Wlmol and AGO = 33.1 kJ/mol at 25OC, above what minimum temperature

will the reaction become spontaneous under standard state conditions?

(A) 104 K (B) 295 K (C) 321 K (D) 401 K (E) 525 K

(21) For the reaction H2(g) + S(s) + H2S(,), AH0 = -20.2 kJ/mol and AS0 = +43.1 J/K-mol. Which of thc following statements is true?

(A) The reaction is only spontaneous at low temperatures.

(B) The reaction is spontaneous at all temperatures.

(C) AGO becomes less favorable as temperature increases.

@) The reaction is spontaneous only at high temperatures.

(E) The reaction is at equilibrium at 25OC under standard conditions.

(22) The substance of A1C13 is considered as

(A) a strong Bronsted acid (B) a weak Bronsted acid

@) a weak Lewis acid (E) a neutral compound

(C) a strong Lewis acid

(23) The half-reaction that occurs at the cathode during electrolysis of an aqueous sodium iodide solution

is:

(A) ~ a + + e + Na (B) Na + ~ a + + e-

(D) + 2 e + 2 r (E) 2 r -+ r2 + 2e-

(24) In the complex ion [co(en)2~r2]+, the oxidation number of Co is

(A) +1 (B) +2 (C> +3 (Dl -2

(C) 2H20 + 2 e + H2 + 20H-

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(25) Consider the following structures (1 and 2 are octahedral; 3 and 4 are square planar).

qp.ON .-. ,X X. -.M.O .A > Qp. ;qy A?' \Y = ethylene diamine

X ' A Y Y I 2 3 4

0 1 Which one of the following statements about the above structures is correct? (A) 1 and 2 are superimposable. (B) 1 and 2 are geometric isomers. (C) 3 and 4 are structural isomers. (D) 3 and 4 are optical isomers.

(E) 3 and 4 are geometric isomers.

(26) Which one of the following statements about fission and fusion is false?

(A) Fission occurs among the heaviest isotopes, whereas ksion occurs more readily for light isotopes.

(B) For a fission reaction the mass defect (Am) is negative, whereas for fusion Am is positive. (C) In order for fusion reactions to occur, temperatures must be in the millions of degrees.

(D) The fission of Pu-239 atoms produces a great number of isotopes of a large number of elements.

(E) Neutron-induced fission processes can occur at room temperature, rather than at millions of

degrees.

(27) How many I4c atoms are in a charcoal sample that has a decay rate of 3,500 disintegrations per min?

(For I4c, t , / ~ = 5,730 yr.)

(A) 2.9 x lo7 atoms (B) 8.0 x 10' atoms (C) 1.4 x 1 o ' ~ atoms

@) 1.5 x l0l3 atoms (E) 6.02 x 1 020 atoms

(28) One can safely assume that the 3s- and 3p-orbitals will form molecular orbitals similar to those formed

when 2s- and 2p-orbitals interact. According to molecular orbital theory, what will be the bond order

for the ~ 1 ; ion?

(A) 0.5 (B) 1.0 (C) 1.5 (D) 2.0 (El 3.0

(11) (a) Explain how the crystal field theory can use the magnitude of the splitting energy (A) to provide an explanation of the color and magnetic properties of octahedral complexes. (3%) .

(b) In promoting an electron from the tz, set of orbitals to the e, set, an octahedral complex absorbs a

photon with a wavelength h of 523 nm. Calculate the value of A in the complex, in kJImol. (3%)

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(111) Scuba diving is an exhilarating sport and is also a safe activity for trained individuals who are in good

health. A typical dive might be 10 to 20 meters, but dives to 30 meters are not uncommon.

(a) What would happen if a diver rose to the surface fiom a depth of 15 meters rather quickly without

breathing? Please use the change in pressure to explain this phenomenon. (3%)

(b) Usually the divers will equip with scuba tank to ensure that the air pressure they breathe equals the

water pressure at all time and inert gas is usually used to dilute oxygen gas for meeting this

purpose. Of various inert gases used, helium (He) gas is the often used gas rather nitrogen (&)

to dilute oxygen gas in scuba tank. Please use Dalton's law and gas solubility to explain why

inert gas is needed to dilute oxygen gas in scuba tank and why helium is better than nitrogen?

(3%)

OV) Ozone is the most important atmospheric gas to protect human beings against UV radiation. Given that

the quantity of ozone in the stratosphere at 26 km is equivalent to a 3.0-mm-thick layer of ozone on

Earth at STP.

(a) Calculate the number of ozone molecules in the stratosphere and their mass by assuming the

radius of Earth is 6370 km. (3%)

(b) In the rnid- 1980s' evidence began to accumulate that an "Antarctic ozone holes" developed in late

winter. Now it is clear that the polar ozone hole is mainly caused by the massive use of

chlorinated compounds such as Freon (chlorofluorocarbons, CFCs). Taking Freon-12 as an

example, explain how CFCs deplete the ozone molecules in the stratosphere? (3%)

(c) If ozone is generated according to the process 302(,) + 203(,), please calculate the wavelength the

oxygen molecules can absorb to convert to ozone. How many ozone molecules can be produced

in the stratosphere at 26 km when oxygen molecules absorb the wavelength? (4%)

Species AH: (kJlm01) AG? OcT/mol) AS: (Jlmol-K)

OW 0 0 205.0

ow 249.2 23 1.7 160.95

03(g) 142.2 163.0 238.82

(V) A quantitative measurement of how efficiently spheres pack into unit cells is called packing efficiency, which is the percentage of the cell space occupied by the spheres. Please calculate the packing efficiencies of a simple cubic cell, a body-centered cubic cell, and a face-centered cubic cell.

(8%)

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(VI) Acetylene (C2H2) has a tendency to lose two protons and form the carbide ion (cz2-), which is present

in a number of ionic compounds, such as CaC2 and MgC2. Please describe the bonding scheme in

the ion in terms of molecular orbital theory. Also compare the bond order c;- with that in C2.

(8%)

(VII) An acidified solution was electrolyzed using copper electrodes. A constant current of 1.1 8 A caused

the anode to lose 0.584 g after 25 min.

(a) What is the gas produced at the cathode and what is its volume at STP? (3%)

(b) Calculate the experimental Avogadro's number. Compare your result with the generally accepted

value of Avogadro's number. (3%)

Note: The atomic masses of elements are as follows:

H = 1.0 He = 4.0 C = 12.0

Na = 23.0 Mg = 24.3 A1 = 27.0

Mn = 54.9 Cu = 63.5 Br = 79.9